Method for working magnetic disk mount portion of motor hub of the hard disk drive apparatus, thus obtained motor hub, and motor including the same

ABSTRACT

A grinding operation is effected by rotating the motor hub in high speed around the central axis thereof, and urging the outer peripheral surface of a grinding wheel rotated in high speed around the central axis against the upper surface of the outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk. The surface of the flange can be worked in high precision. Thus, a compact, large capacity, and reliable hard disk drive apparatus is to be provided by reducing the rotational runout of the magnetic disk incorporated within the hard disk drive apparatus.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates to a method for working a magnetic disk mount portion of a motor hub of the hard disk drive apparatus, a motor hub manufactured through such method, and a motor including such motor hub,

[0003] 2. Description of the Prior Art

[0004] The hard disk drive apparatus is used extensively as an internal or external memory of computers, and the capacity required for the hard disk drive apparatus has increased with the years. Further, the apparatus must be produced in low cost and in compact.

[0005] Thus the trucks defined on the magnetic disk of the hard disk drive apparatus are densified more and more so that it becomes necessary to rotate the magnetic disk correctly in order to facilitate the access of the magnetic head to the intended truck on the magnetic disk.

[0006] The countermeasures taken in the prior art to improve the accuracy of rotation of the magnetic disk are the improvement of the accuracy of the machining operation to be effected on the motor hub to which magnetic disk or disks are to be incorporated, the improvement of the accuracy of the rotation of the bearing of the motor for driving the disks, and the improvement of the accuracy on assembling the elements of the motor, as well as the countermeasures against resonance frequency.

[0007] However, these countermeasures are known insufficient to deal with the problems accompanied with the densification of the trucks. The essential conditions in solving these problems are high evenness or flatness of the magnetic disk mounted on the motor hub and the reduction of the waveform deflection.

[0008] The above-mentioned essential conditions are for inhibiting the rotational runout of the magnetic disk upon utilized the hard disk drive apparatus. It is especially necessary to satisfy the above mentioned conditions in the case in which the hydraulic bearing are used in the journaling portion of the motor.

[0009] In satisfying the above-mentioned conditions, it is necessary to improve the accuracy of the worked motor hub or of the disk supporting surface on which the magnetic disks are mounted.

[0010] Generally, the motor hub is manufactured through the cutting operation since the cutting operation can be effected easily Ad through fewer steps.

[0011] During cutting, the work or the motor hub is rotated in high speed, and the surface to be worked is to be cut through the contact with the cutting tool. The accuracy of the working on the surface to be worked depends on the precision of the rotation of the work during working. In other words, the rotational runout of the work will present the deflection of the surface to be worked.

[0012] In conclusion, the accurate working through the cutting operation is cumbersome or difficult, and requires more cost. This is because the cutting device of high precision is required, and the conditions for cutting such as the number of rotation of the work, the feed rate of the cutting tool, and the shape of the cutting tool must be set and maintained in strict manner.

OBJECT OF THE INVENTION

[0013] It is an object of the present invention to work a disk supporting surface of the motor hub of the hard disk drive apparatus in high precision and easily. This will reduce the rotational runout of the magnetic disk. Thus, a compact, large capacity, and reliable hard disk drive apparatus can be realized,

SUMMARY OF THE INVENTION

[0014] A method for working a magnetic disk mount portion of a motor hub of the hard disk drive apparatus including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the method being characterized in that the motor hub is rotated in high speed around the central axis thereof, and outer peripheral surface of a grinding wheel rotated in high speed around the central axis thereof is urged on the upper surface of the outwardly extending flange.

[0015] The method for working a magnetic disk mount portion of the motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub through the displacement of the carriage.

[0016] The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage.

[0017] The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage as well as the displacement of the carriage.

[0018] A method for working a magnetic disk mount portion of a motor hub of the hard disk drive apparatus including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the method being characterized in that;

[0019] the motor hub is rotated in high speed around the central axis thereof, and the grinding wheel is also rotated in high speed around the central axis thereof, the grinding wheel includes a pair of tapered surfaces extending axially outwardly to reduce the diameter thereof and orthogonal with each other from an edge defined at the intersection of the tapered surfaces, wherein the grinding operation is effected by urging the tapered surfaces against the disk fitting surface and the upper surface of the outwardly extending flange respectively.

[0020] The method for working a magnetic disk mount portion of the motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub through the displacement of the carriage.

[0021] The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage.

[0022] The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage as well as the displacement of the carriage.

[0023] A motor hub of the hard disk drive apparatus comprising a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the motor hub being characterized in that:

[0024] the motor hub is rotated in high speed around the central axis thereof, and the upper surface of the outwardly extending flange is adapted to be ground by the outer peripheral surface of the grinding wheel rotated in high speed around the axis thereof.

[0025] The motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.

[0026] The motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.

[0027] The motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage.

[0028] A motor hub of the hard disk drive apparatus comprising a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the motor hub being characterized in that:

[0029] the motor hub is rotated in high speed around the central axis thereof, and the grinding wheel is also rotated in high speed around the central axis thereof, the grinding wheel includes a pair of tapered surfaces extending axially outwardly to reduce the diameter thereof and orthogonal with each other from an edge defined at the intersection of the tapered surfaces, wherein the grinding operation is effected by urging the tapered surfaces against the disk fitting surface and the upper surface of the outwardly extending flange respectively.

[0030] The motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.

[0031] The motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.

[0032] The motor hub of the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displayable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage.

[0033] A motor for the hard disk drive apparatus including a motor hub around the outer periphery of which a magnetic disk or a plurality of magnetic disks are to be provided, the motor hub is journalled on a base through a bearing apparatus, the motor being characterized in that the motor hub is provided with a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, wherein the upper surface of the outwardly extending flange of the motor hub rotated in high speed around the central axis thereof is adapted to be ground by an outer peripheral surface of a grinding wheel rotated in high speed around the central axis thereof.

[0034] The motor for the hard disk drive apparatus according to the present invention is characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.

[0035] The motor for the hard disk drive apparatus according to the present invention, characterized in that said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.

[0036] The motor for the hard disk drive apparatus according to the present invention, characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage

[0037] A motor for the hard disk drive apparatus including a motor hub around the outer periphery of which a magnetic disk or a plurality of magnetic disks are to be provided, the motor hub is journalled on a base through a bearing apparatus, the motor being characterized in that the motor hub is provided with a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, wherein the disk fitting surface and the upper surface of the outwardly extending flange of the motor hub rotated in high speed around the central axis thereof are adapted to be ground by a pair of tapered surfaces of a grinding wheel rotated in high speed around the central axis thereof, the tapered surfaces extending axially outwardly with reducing the diameter thereof from an edge define a right angle at the edge defined therebetween.

[0038] The motor for the hard disk drive apparatus according to the present invention, characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.

[0039] The motor for the hard disk drive apparatus according to the present invention, characterized in that said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.

[0040] The motor for the hard disk drive apparatus according to the present invention, characterized in that said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Further feature of the present invention will become apparent to those skilled in the art to which the present invention relates from reading the following specification. with reference to the accompanying drawings, in which:

[0042]FIG. 1 is a vertical cross sectional view showing a motor hub of the present invention;

[0043]FIG. 2 is a partially broken elevational view showing a process for working in accordance with the present invention;

[0044]FIG. 3 is a partially broken elevational view showing the other process for working in accordance with the present invention;

[0045]FIG. 4 is a vertical cross sectional view showing a motor of the present invention and magnetic disks assembled therewith; and

[0046]FIG. 5 is a vertical cross sectional view showing a motor of another embodiment of the present invention and magnetic disks assembled therewith.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0047] A method for working a magnetic disk mount portion of a motor hub in accordance with the present invention will now be described with reference to the attached drawings.

[0048] The shape of a motor hub of the hard disk drive device may vary depending on the number of the magnetic disks to be mounted around the hub, the size of the hard disk drive device itself, or the structure of the motor. An example of the shape of the motor hub is shown in FIG. 1 only as an illustrative example. As shown in FIG. 1, a hub 1 is provided with a central aperture 2 to be fit around the spindle of the motor. The hub also includes a skirt 3 extending downwardly from the outer periphery thereof, and a flange 4 extending outwardly from the lower edge of the skirt 3. An undercut 5 is formed on the upper surface of the flange 4.

[0049] The outer peripheral surface of the downwardly extending skirt 3 is a disk fitting surface A, and the upper surface of the outwardly extending flange 4 is a disk supporting surface B. These surfaces A and B constitute a mount for a magnetic disk or disks.

[0050] The hub 1 is worked preliminary by cutting it to the predetermined size and shape. The hub will then be secured to a clamping fixture 6 by inserting a spindle 6 a of the fixture through the central aperture 2 of the hub and tightening a nut 7 onto the thread provided at the distal end of the spindle. The undercut 5 is also formed preliminary by cutting operation.

[0051] A sand grinding stone 8 to be employed for grinding a pair of tapered surfaces 8 a, 8 b extending axially outwardly from the outer peripheral edge so as to reduce the diameter thereof. The generatrices of the tapered surfaces 8 a, 8 b are intersected in right angle with each other.

[0052] A grinding apparatus 9 for operating the grinding stone 8 includes a rotationally driving apparatus 11 mounted on a carriage 10 so as to be displaceable in X, Y, and Z directions. The stone 8 is attached to a spindle 12 of the rotationally driving apparatus. The contact angle of the stone 8 with the hub 1 can be adjusted by controlling swinging movement of the rotationally driving apparatus 11 relative to the carriage 10 about an axis 11 a extending orthogonal to the spindle 6 a of the clamping fixture.

[0053] The grinding stone is adapted to be rotated in high speed by the grinding apparatus 9 of the structure as mentioned above. During the grinding operation, the angle of the grinding stone relative to the hub can be set no as to make each of the pair of tapered surfaces 8 a, 8 b parallel to the surfaces A and B respectively. The hub 1 is also rotated in high speed around the central axis thereof by driving the clamping fixture 6.

[0054] The disk fitting surface A and the disk supporting surface B can be leveled by urging the grinding stone 8 against the surfaces A and B through shifting the carriage 10 in the vertical and/or horizontal directions.

[0055] The grinding operation can also be effected by swinging the grinding stone 8 around the axis 11 a.

[0056] In the above-mentioned grinding operation, the hub 1 is rotated in high speed to be worked and the grinding stone 8 corresponding to the cutting tool employed for the cutting operation. In this connection, even if the rotational runout phenomena is caused on the hub as well as the grinding stone, these elements are adapted to be contacted with each other in the peak of the stroke of the runout, so that essentially no effects are caused by the rotational runout of the elements on the accuracy of the processing of the surfaces such as the disk fitting surface A and the disk supporting surface B.

[0057] The feed rate of the grinding stone can be adjusted finely so that the resistance encountered on grinding can be controlled to be minimum. In this connection, the grinding operation can provide a surface by far smoother than that obtained through the cutting operation.

[0058] In other words, the accuracy on working the disk fitting surface A and the disk supporting surface B can be enhanced dramatically relative to that obtained by cutting operation, so that the wave-shaped deformation on the disk supporting surface B can be reduced to the minimum.

[0059] Further, in the grinding operation, the roughness on the ground surface can be adjusted arbitrarily through the selection of the grinding wheel 8.

[0060] In the above-mentioned embodiment, the grinding operation is adapted to be effected by displacing the grinding stone 8 relative to the side of the hub 1. Whereas, the grinding operation can also be effected by displacing the hub 1 toward the grinding atone in the direction vertical to the spindle so as to urge the disk fitting surface A against the tapered surface 8 a of the grinding stone, and by displacing the hub 1 in the axial direction to grind the disk supporting surface B by the tapered surface 8 b of the grinding stone.

[0061] Further, in the above mentioned embodiment, the disk fitting surface A and the disk supporting surface B are to be ground at the same time by using a forming grinding stone 8. Whereas, sometimes only the disk supporting surface B is adapted to be polished by a column shaped grinding stone 13 as shown in FIG. 3.

[0062] An embodiment of a motor including the hub of the structure as mentioned above will now be described with reference to FIG. 4 in which magnetic disks are to be provided around the hub.

[0063] The hub 1 is adapted to be journalled by means of a bearing apparatus 15 comprising a stepped shaft 16 including an enlarged diameter shaft portion 16 a and a reduced diameter shaft portion 16 b, a sleeve outer ring 17, and two rows of balls 18, 19 interposed between the shaft and the ring.

[0064] The outer periphery of the enlarged diameter shaft portion 16 a is provided with an inner ring raceway 20 a for the one row of the balls 18. Fit around the reduced diameter shaft portion 16 b is an inner ring 21 around the outer periphery of which is provided with an inner ring raceway 20 b for the other row of the balls 19. Provided on the inner peripheral surface of the sleeve outer ring are an outer ring raceway 22 a for the one row of the balls 18 and an outer ring raceway 22 b for the other row of the balls 19. What is designated by the reference numeral 23 is a retainer.

[0065] In the above mentioned structure of the bearing apparatus 15, no inner ring is required for the one row of balls since the inner ring raceway 20 a is formed directly on the enlarged diameter shaft portion 16 a. Thus the diameter of the shaft can be enlarged in that portion to enhance the rigidity of the shaft. The rotational runout and the oscillation of the shaft can also be reduced. Further, the accuracy of the rotation can be enhanced by urging the inner ring 21 upwardly to provide a suitable pre-load on the ball.

[0066] The sleeve outer ring 17 is fit and secured into the bearing holder 24 protruding upwardly from the central portion of a base 14. The hub 1 is fit and secured at its central opening 2 around the upper end of the stepped shaft 16.

[0067] Provided around the bearing holder 24 are a plurality of stators 26 each of which a coil 25 is wounded therearound. A plurality of magnets 27 is provided on the inner surface of the downwardly extending skirt 3 of the hub 1 so as to oppose to the stators 26.

[0068] In Fig, 4, those designated by the reference numeral 28, 28 are magnetic disks fit at their central opening 28 a around the disk fitting surface A of the downwardly extending skirt 3. The magnetic disks are spaced apart from each other by interposing an annular spacer 29 therebetween. The assembly comprising magnetic disks and the spacers is sandwiched and secured between the disk supporting surface B of the outwardly extending flange 4 and a disk retainer plate 30, The retainer plate 30 is fixed on the upper surface of the hub by screws 31, 31.

[0069] In the motor of the structure as mentioned above, the flatness of the magnetic disks 28, 28 can be assured in high level, and the runout of the surface of the magnetic disks can also be suppressed, since the disk fitting surface A and the disk supporting surface B of the hub 1 is ground worked accurately by the working process as described above.

[0070] Another embodiment of the motor in accordance with the present invention will now be described with reference to FIG. 5. This motor is different from the motor of the above-mentioned embodiment in the following points:

[0071] (1) a hub 32 and a shaft 33 are formed integrally with each other of the same material; and

[0072] (2) a shaft is journalled through a pair of upper and lower ball bearings 34, 34.

[0073] To say concretely, the hub 32 includes the hollow cylindrical straight shaft 33 extending downwardly from the central portion of the lower surface thereof. The shaft 33 is fit and secured within inner races 34 b, 34 b of the ball bearings 34, 34. Outer races 34 a, 34 a of the ball bearings 34, 34 are fit and secured within the bearing holder 24.

[0074] In the motor of the structure as mentioned above, it is unnecessary to assemble the hub with the shaft since these elements are formed integrally with each other of the same material. Thus, it is also unnecessary to consider how accurately assembled the hub with the shaft. This also leads to the advantage that the number of steps required for manufacturing the motor can be reduced.

[0075] The elements of the motor illustrated in FIG. 5 other than those mentioned above are same as those of the motor illustrated in FIG. 4.

[0076] In accordance with the present invention, the resistance produced between the grinding stone and the surface to be worked can be controlled to the much lower value than that caused by the cutting operation, since grounded is the surface for supporting the magnetic disk or the upper surface of the outwardly extending flange. Further, the runout of the work on the working process hardly affects the accuracy of working, since the motor hub or the work and the grinding stone are rotated in high speed during working. Thus the surface for supporting the magnetic disk can be worked to have high flatness. The motor hub including the surface for supporting the magnetic disk worked in high precision can support the magnetic disk or disks stably without compromising the flatness of the magnetic disk.

[0077] In the motor including the above-mentioned hub, the runout of the surface of the magnetic disk upon rotation can be reduced to the minimum. In this connection, the magnetic head can be accesses accurately to the required truck of the magnetic disk, and the hard disk drive apparatus can be miniaturized and the storage capacity of the apparatus can be enlarged.

[0078] While particular embodiments of the present invention have been illustrated and described, it should be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. 

What is claimed is:
 1. A method for working a magnetic disk mount portion of a motor hub of the hard disk drive apparatus including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the method being characterized in that: the motor hub is rotated in high speed around the central axis thereof, and outer peripheral surface of a grinding wheel rotated in high speed around the central axis thereof is urged on the upper surface of the outwardly extending flange.
 2. The method for working a magnetic disk mount portion of the motor hub of the hard disk drive apparatus as claimed in claim 1, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub through the displacement of the carriage.
 3. The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus as claimed in claim 1, wherein said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage.
 4. The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus as claimed in claim 1, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage as well as the displacement of the carriage.
 5. A method for working a magnetic disk mount portion of a motor hub of the hard disk drive apparatus including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the method being characterized in that: the motor hub is rotated in high speed around the central axis thereof, and the grinding wheel is also rotated in high speed around the central axis thereof, the grinding wheel includes a pair of tapered surfaces extending axially outwardly to reduce the diameter thereof and orthogonal with each other from an edge defined at the intersection of the tapered surfaces, wherein the grinding operation is effected by urging the tapered surfaces against the disk fitting surface and the upper surface of the outwardly extending flange respectively.
 6. The method for working a magnetic disk mount portion of the motor hub of the hard disk drive apparatus as claimed in claim 5, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub through the displacement of the carriage.
 7. The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus as claimed in claim 5, wherein said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage.
 8. The method for working the magnetic disk mount portion of the motor hub of the hard disk drive apparatus as claimed in claim 5, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the grinding wheel is urged against the magnetic disk mount portion of the hub by pivoting the rotationally driving apparatus with respect to the carriage as well as the displacement of the carriage.
 9. A motor hub of the hard disk drive apparatus comprising a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the motor hub being characterized in that: the motor hub is rotated in high speed around the central axis thereof, and the upper surface of the outwardly extending flange is adapted to be ground by the outer peripheral surface of the grinding wheel rotated in high speed around the axis thereof.
 10. The motor hub of the hard disk drive apparatus as claimed in claim 9, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.
 11. The motor hub of the hard disk drive apparatus as claimed in claim 9, wherein said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.
 12. The motor hub of the hard disk drive apparatus as claimed in claim 9, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage.
 13. A motor hub of the hard disk drive apparatus comprising a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, the motor hub being characterized in that: the motor hub is rotated in high speed around the central axis thereof, and the grinding wheel is also rotated in high speed around the central axis thereof, the grinding wheel includes a pair of tapered surfaces extending axially outwardly to reduce the diameter thereof and orthogonal with each other from an edge defined at the intersection of the tapered surfaces, wherein the grinding operation is effected by urging the tapered surfaces against the disk fitting surface and the upper surface of the outwardly extending flange respectively.
 14. The motor hub of the hard disk drive apparatus as claimed in claim 13, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.
 15. The motor hub of the hard disk drive apparatus as claimed in clam 13, wherein said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.
 16. The motor hub of the hard disk drive apparatus as claimed in claim 13, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so an to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage.
 17. A motor for the hard disk drive apparatus including a motor hub around the outer periphery of which a magnetic disk or a plurality of magnetic disks are to be provided, the motor hub is journalled on a base through a bearing apparatus, the motor being characterized in that the motor hub is provided with a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, wherein the upper surface of the outwardly extending flange of the motor hub rotated in high speed around the central axis thereof is adapted to be ground by an outer peripheral surface of a grinding wheel rotated in high speed around the central axis thereof.
 18. The motor for the hard disk drive apparatus as claimed in claim 17, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.
 19. The motor for the hard disk drive apparatus as claimed in claim 17, wherein said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.
 20. The motor for the hard disk drive apparatus as claimed in claim 17, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage.
 21. A motor for the hard disk drive apparatus including a motor hub around the outer periphery of which a magnetic disk or a plurality of magnetic disks are to be provided, the motor hub is journalled on a base through a bearing apparatus, the motor being characterized in that the motor hub is provided with a magnetic disk mount portion including a cylindrical disk fitting surface around which a central aperture of a magnetic disk or disks are to be fit, and an outwardly extending flange for supporting on its upper surface the lower surface of the central portion of the magnetic disk, wherein the disk fitting surface and the upper surface of the outwardly extending flange of the motor hub rotated in high speed around the central axis thereof are adapted to be ground by a pair of tapered surfaces of a grinding wheel rotated in high speed around the central axis thereof, the tapered surfaces extending axially outwardly with reducing the diameter thereof from an edge define a right angle at the edge defined therebetween.
 22. The motor for the hard disk drive apparatus as claimed in claim 21, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, wherein the magnetic disk mount portion of the hub is ground through the displacement of the carriage.
 23. The motor for the hard disk drive apparatus as claimed in claim 21, wherein Said grinding wheel is attached to the spindle of the rotationally driving apparatus connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage.
 24. The motor for the hard disk drive apparatus as claimed in claim 21, wherein said grinding wheel is attached to a spindle of the rotationally driving apparatus connected to the carriage displaceable in X, Y, and Z directions, and the rotationally driving apparatus is connected to the carriage so as to pivot around the axis extending orthogonal to the central axis of the motor hub, wherein the magnetic disk mount portion of the hub is ground by pivoting the rotationally driving apparatus with respect to the carriage, and by displacing the carriage. 